1 Background

Nature of HIV infection

1.1 We begin our report with a brief description of the nature of HIV infection. First, three points about the duration of infection and its implications:
a. on theoretical grounds, infection will be lifelong;
b. on current understanding, treatment at present and in the immediate future will at best be likely only to contain rather than eradicate infection;
c. future vaccines, if ever available, will not be available in a public health role until the mid 1990s at the earliest.
Therefore infection is, apparently, irreversible and primary preventive efforts are of supreme importance. For the forseeable future, this infection will only be contained if educational efforts are successful and risk behaviour is significantly modified.

1.2 Since infection is lifelong, the proportion of infected patients who develop AIDS or other life threatening diseases, may not be determined for several decades. Homosexual men are the most studied population; various cohort studies have shown that rates of 8 to 10 per cent per year, after 3 years, will progress to AIDS so that by 5 years 30 to 35 per cent have developed AIDS. Some studies have shown that given time the vast majority of patients will show deterioration in their immune system. The rate of progression in injecting drug misusers is likely to be at least as great as in homosexuals.

1.3 In view of the variation in rates of progression, there is much scientific interest in the role of various co-factors which may either induce or hasten the development of AIDS. Current research suggests that exposure to other infectious agents may reactivate HIV in infected cells leading to increased viral production, dissemination and progression. Amongst additional suggested co-factors are continued injecting drug misuse, chronic anxiety and depression, and pregnancy (although there is conflicting evidence on this). If validated, all of these co-factors are relevant to the drug misuse problem. Of particular potential importance is work in New York amongst HIV positive drug misusers which indicates that continued non-sterile injection with impure street drugs leads to deterioration in immune status (as measured by numbers of helper T cells — those white blood cells specifically infected by HIV and involved in defence against some infections), compared to a control group of methadone-treated, infected users. Furthermore other evidence is emerging that further deterioration in immune status is associated with increased viral load (as detected in HIV antigen testing) and enhanced infectivity by injecting and sexual activity. Other work has shown that there appears to be an increased rate of transmission to the heterosexual partners of haemophiliacs whose disease had progressed to the stage that they had a marked reduction in their helper T cells. Therefore management which reduces the use of injected street drugs will have a most important role in the context of public health as well as individual health.

1.4 The spectrum of HIV diseases continues to increase, as is recognised in the new Centers for Disease Control (Atlanta) classification scheme. This is reflected in the continued expansion of the surveillance criteria for the diagnosis of AIDS. Nevertheless, it is possible that significant numbers of deaths will occur in seropositive injecting drug misusers due to conditions such as bacterial pneumonia and septicaemia which would not satisfy present criteria of AIDS, but are related to their HIV infection. HIV disease may also manifest through mechanisms other than immunosuppression. The most important examples of this are the direct neurological effects of HIV especially dementia. Dementia is a well recognised complication in AIDS and compounds the problems of management of injecting drug misusers with HIV related disease.

1.5 Currently there are increasing numbers of sick HIV positive patients undergoing long term therapy with Zidovudine (AZT, `Retrovir'). This is a toxic, costly drug which makes major demands on patient compliance. It would appear to have a palliative role in serious HIV disease, in improving the quality of life over the short term in those who can tolerate it. In seropositive patients the therapeutic benefit of long term therapy has yet to be determined. The introduction of other less toxic therapies may alter this position, as might evidence that anti-retroviral therapy would reduce infectivity by any of the modes of transmission.

Spread of HIV and AIDS through Drug Misuse

1.6 We have noted that HIV can be passed between injecting drug misusers who share needles, syringes or other equipment which have become contaminated with infected blood. This is a major route of transmission of the virus and in some European countries the majority of cases of AIDS (Italy and Spain) or HIV infection (Scotland) have occurred through the use of contaminated injecting equipment.

1.7 In the UK, by the end of December 1987, 19 out of 1227 cases of AIDS were attributed to shared injecting practice among drug misusers. Of some 8000 people in the UK who have been found to be seropositive, almost 1300 have been injecting drug misusers. It is likely that these may represent only a small proportion of the total infected. Within these totals, Scotland accounts for just over 1300 antibody positive reports of which some 750 arise from injecting drug misuse. Some local studies in Edinburgh have found HIV seroprevalence levels of around 50 per cent amongst injecting drug users. Conversely, some small scale studies in a number of English cities have suggested seroprevalence rates of between nil and 10 per cent. These regional and local variations are mirrored in other parts of the world. In the United States, for example, seroprevalence amongst injecting drug users is estimated to range from 50 per cent to 70 per cent in New York to under 2 per cent in some other States. The reasons for such variations are not fully understood, but include the date of introduction of the virus into the local drug misusing population, and the extent of sharing of equipment.

1.8 In the UK, as in many other countries, injecting drug misuse has so far been the route of acquisition of HIV for the majority of infected women, most of whom are of child-bearing age (the vast majority in Scotland). And infected women are now giving birth to children in significant numbers. At the time of writing some 80 babies with antibodies to HIV in their blood have been born in the UK to antibody positive mothers. Whilst the presence of antibodies in a baby's blood at birth is not an accurate guide to infection, many of these children have developed, or are likely to develop, the infection and several have already died of AIDS.

1.9 Infected drug misusers can transmit HIV sexually as well as by sharing injecting equipment. Since the vast majority of drug misusers in the UK are thought to be heterosexual, sexual transmission will be an important route from them into the general heterosexual population. In one study in New York, where the virus is well established amongst injecting drug misusers, injecting drug misusers were thought to have been the source of the virus in 87 per cent of cases in which heterosexual activity was believed to be the mode of transmission.

1.10 Disturbing as the UK figures are, they do suggest that outside a small number of locations (notably Edinburgh) the virus may not yet be well established in the drug injecting community. This means that vigorous preventive measures taken now stand a good chance of stemming the spread of the virus. But the need for immediate action cannot be overstressed. The experience of Edinburgh, where the prevalence of HIV amongst injecting drug users rose to around 50 per cent within 2 years of the first seropositive sample, illustrates how rapidly the virus can spread. And the American experience — where in New York alone by the beginning of 1987, there were 3000 cases of AIDS amongst heterosexual injecting drug misusers — illustrates the potential scale of the disaster if we fail to act effectively. In the USA as a whole, a quarter of the 50,000 cases of AIDS have occurred in drug misusers, a minority of whom have also had homosexual risk activity. In Europe the proportion of cases of AIDS which has occurred in drug misusers has risen from 2 per cent in 1984 to 17 per cent in 1987 with much higher trends in some countries and cities. The future scale of the American problem has been dramatically underlined by the Coolfont Conference of AIDS experts in 1986. This group issues projections that by 1991, 270,000 cases of AIDS will have occurred in the United States. It is likely that 50,000 to 80,000 cases will have occurred in drug users and that there will be about 7000 cases due to heterosexual transmission and 3000 due to foetal transmission.

Other Viruses

1.11 There are now known to be at least 2 members of the human immunodeficiency virus family, HIV-1 (the cause of most disease in the epidemic so far) and HIV-2. The latter virus appears to cause disease of similar severity but is at present only known to be prevalent in a few West African countries. However, occasional cases are being found elsewhere. Dual infection may occur. Continued vigilance will be necessary to detect whether HIV-2, or any subsequently described HIV variants, are entering the injecting drug misuse population. Fortunately, measures to prevent the spread of HIV-1 will work in the same way with HIV-2. In addition there are other known (and probably unknown) viruses whose spread will also be reduced by the measures we are advocating. These viruses include HTLV-1 (human T cell lymphotropic virus), HTLV-2, and a variety of hepatitis viruses including hepatitis B, non-A non-B virus and delta agent.

Interaction of these viruses with each other may cause a variety of clinical outcomes but all are potentially important.

Pattern and Prevalence of Drug Misuse

1.12 In order to devise effective measures to counter the spread of HIV, and other viruses, through injecting drug misuse it is necessary to have some understanding of the pattern and scale of drug misuse. The illicit and hidden nature of the activity means it is impossible to obtain a completely accurate picture, or indeed to be certain about the accuracy of any picture. However, information about drug misusers who seek help from services, together with information on arrests and seizures, can be used in conjunction with research findings to gain some impressions about the scale and nature of drug misuse. The limitations of our information base, and ways of improving it, are discussed in Chapter 8. For the present, we concentrate on what information is available.

1.13 Doctors are statutorily required to notify in confidence the Chief Medical Officer at the Home Office when they attend a patient whom they suspect or believe to be addicted to certain controlled drugs (princip.'lly various opioids and cocaine). In 1986 the total number of drug misusers notified in this way (including new and re-notifications and those receiving treatment at the beginning of the year) was nearly 15,000. It is widely accepted however that the annual number of notified addicts underestimates the total population of users of notifiable drugs during that year. Local prevalence studies, using a variety of case-finding methods and conducted in different years have suggested that at times notifications may represent only 10-20 per cent of notifiable drug users, while in others 50 per cent of the users located were found to have been notified as addicts at some time. Given the extent of local variations both in the prevalence of drug misuse and in the numbers notified, changes over time in incidence rates in the same area, and the availability and effectiveness of treatment, our best guess is that there might have been between 75,000 and 150,000 misusers of notifiable drugs in the UK during 1986. In addition there may be as many again (excluding cannabis users) who are using a variety of non-notifiable drugs (such as amphetamine) on an experimental or occasional basis. Home Office statistics for 1986 show that there have been continuing annual increases in the quantity of amphetamine seized. In parallel with this, anecdotal evidence and local research studies suggest that amphetamine is now widely misused and may be the main drug of misuse in some areas. Moreover, use by injecting, on an occasional or regular basis is widely reported and appears to be on the increase.

1.14 Within this very broad picture of the scale of drug misuse, the pattern of misuse is complex. Many drug misusers will switch from one drug to another if their drug of first choice becomes too expensive or hard to obtain locally. Some misuse one drug at at time, others may be misusing several at any given time. Similar complexities apply to the method of administration. There are many shades of grey between a drug misuser who never injects and a drug misuser who always injects. Many people who misuse drugs primarily by inhalation or swallowing also inject drugs occasionally. One factor often mentioned here is price and availability: when a drug is scarce and expensive many misusers prefer to inject so as to maximise the effect of the limited amount they have been able to obtain. Most drug misusers in England begin their drug misuse by inhalation but many progress to injecting, probably passing through several stages. Halting this progression to injecting is of key importance in curbing the spread of HIV.

1.15 These variations in drug use and method of administration make it very hard to quantify the number of people who may be misusing drugs by injection. Anecdotal and research evidence up until mid-1987 suggests that, depending on the area studied, between 0 per cent and 90 per cent of opioid misuses may predominately use by injection. Over the country as a whole therefore, we have assumed that about half of all opioid misusers may at some time inject. On this basis, in 1986 there may have been between 37,000 (half of 75,000) and 75,000 (half of 150,000) injectors of notifiable drugs in the UK supplemented by a pool of injectors of other drugs (particularly amphetamines).

1.16 Reliable data on sharing of injecting equipment is also difficult to find but a number of recent studies with injecting drug misusers suggest that the vast majority have shared equipment at some time either regularly or occasionally. This was borne out by the anecdotal evidence presented by witnesses working with drug misusers. One recent study indicated a major drop in sharing amongst attenders at one London drug clinic and many witnesses from drug agencies reported reductions in sharing, though significant levels of sharing continued in many places. Another study, which preceded the Government's current publicity campaign, found little reduction in sharing amongst injecting misusers who are not in contact with services. Factors associated with sharing equipment require further study, but the non-availability of clean equipment (either generally, or just at the time and place of injection) and the view that sharing is the social norm in some drug injecting sub-cultures, are of importance.

1.17 In conclusion, the following points about the scale and pattern of drug misuse are important in devising a strategy to combat the spread of HIV:

a. during 1986 many misusers of certain controlled drugs were likely to do so by injection. Almost all of those who inject either regularly or occasionally will have shared equipment at some time and many continue to do so;
b. injecting drug use is not confined to the opioids; there is some research and anecdotal evidence that amphetamines and other drugs are also injected;
c. patterns of drug use, and method of administration, vary considerably over time between and within different areas;
d. injecting drug use is not confined to persistent regular injectors; a large number of misusers inject drugs occasionally while retaining inhalation or swallowing as their main method of use.
Preventing or halting an individual's progression from inhalation or swallowing to injection is an effective way of combating the spread of HIV.